Reflective platen

ABSTRACT

A platen having a wall defining a reflective supporting surface upon which a first sheet of material is to be supported for exposure of graphic intelligence on the first sheet by directing light toward the platen and first sheet to afford reproduction of said graphic intelligence on a second sheet. The wall may be formed with a multiplicity of orifices communicating between the first sheet on the supporting surface and a means for reducing air pressure in the orifices to attract the first sheet to the platen. A recess in the supporting surface defined by a converging wall is formed about each orifice. The converging wall is formed to reflect incident light through the discontinuity in the supporting surface defined by the recess in generally an even intensity across the discontinuity and with generally the same intensity as light is reflected by the supporting surface thereby destroying the reflected image of the orifices and recesses at the supporting surface.

United States Patent Sagawa [451 July 18, 1972 [54] REFLECTIVE PLATEN[72] Inventor:

[73] Assignee:

Burt K. Sagawa, Bloomington, Minn.

Minnesota Mlling and Manufacturing Company, Saint Paul, Minn.

[22] Filed: April 20, 1971 [21] Appl. No.: 135,704

[52] US. Cl ..355/91, 355/73, 355/76,

355/1 10 [5 1] Int. Cl. ..G03b 27/20 [58] Field ofSearch ..355/73, 76,91, 94

[56] References Cited Assistant Examiner-Richard M. SheerAttorney-Kinney, Alexander, Sell, Steldt & Delahunt ABSTRACT A platenhaving a wall defining a reflective supporting surface upon which afirst sheet of material is to be supported for exposure of graphicintelligence on the first sheet by directing light toward the platen andfirst sheet to afford reproduction of said graphic intelligence on asecond sheet. The wall may be formed with a multiplicity of orificescommunicating between the first sheet on the supporting surface and ameans for reducing air pressure in the orifices to attract the firstsheet to the platen. A recess in the supporting surface defined by aconverging wall is formed about each orifice. The converging wall isformed to reflect incident light through the discontinuity in thesupporting surface defined by the recess in generally an even intensityacross the discontinuity and with generally the same intensity as lightis reflected by the supporting surface thereby destroying the reflectedimage of the orifices and recesses at the supporting surface.

10 Clains, 4 Drawing ligures Patented July 18, 1972 INVENTOR. [BU/Q7 K544mm W w M A 7' T OFPNE Y5 REFLECTIVE PLATEN BACKGROUND OF THEINVENTION This invention relates to a platen formed for supporting afirst sheet in a position for reflex exposure to produce an image of thefirst sheet on a second sheet, and in one aspect to a platen which isformed for even reflectivity at its supporting surface despitediscontinuities in its supporting surface.

The use of a platen for supporting an original sheet of material forexposure by light to afford reproduction of graphic intelligence thereonis common in prior art copying devices.

One type of prior art device for copying graphic intelligence from afirst or original sheet positions the original sheet between thereflective supporting surface of a platen and a translucent intermediatesheet material with the graphic intelligence to be copied disposedadjacent the intermediate sheet. Light is passed through theintermediate sheet to the original sheet. A light sensitive coating onthe intermediate sheet is differentially exposed (desensitized) in apattern corresponding to the graphic intelligence on the original sheetbecause of differences between the percentages of incident lightreflected back through the intermediate sheet from the graphicintelligence and the percentage reflected from the background on theoriginal sheet, the background typically being more reflective than thegraphic intelligence. The intermediate sheet is subsequently processedwith a copy sheet to form a'copy of the graphic intelligence on theoriginal sheet.

If the original sheet copied in such a device has a smaller surface areathan the copy sheet, it is desirable that the supporting surface of theplaten reflect as much light as the background of the original sheetthrough the intermediate sheet to produce a uniform background on thecopy sheet. If under this condition the supporting surface is not asreflective as the background of the original sheet, or if all areas onthe supporting surface do not reflect generally the same percentage ofthe exposure light, these differences in reflectivity will result in acorresponding pattern appearing on the copy sheet.

One prior art means which has been used in devices of this type forcontrolling the position of an original sheet with respect to thesupporting surface of a platen includes controlling the air pressurebetween the original sheet and the supporting surface. The platen isfonned with a multiplicity of orifices oriented at right angles to thesupporting surface and communicating between the supporting surface anda source of pressure variable above or below atmospheric pressure tohold or release the original sheet with respect to the supportingsurface. These orifices provide no reflection of light passing throughthem, thus contrast in reflectivity with adjacent portions of thesupporting surface, and will produce a corresponding print of theorifices on portions of the intermediate not separated from the platenby an original sheet, and on a portion of a copy sheet which is largerthan the original sheet. Such patterns are aesthetically undesirable tousers of the copy machine.

SUMMARY OF THE INVENTION The supporting surface of a platen madeaccording to the present invention may be formed with discontinuitiescomprising orifices communicating with the supporting surface withoutproducing a print of the discontinuities on a copy sheet which is largerthan an original sheet.

On a platen made according to the present invention means interactingbetween the platen and an original sheet such as an orifice, orswitching or signal means, may be located in a specially formed recessin the wall defining the supporting surface. The recess is defined byconverging wall means which reflect incident light through thediscontinuity defined by the recess in the supporting surface withgenerally an even intensity across the discontinuity and with generallythe same intensity as light is reflected from the supporting surface.The platen may thus provide a background on an entire copy sheet whichis essentially even in exposure with the background of a smalleroriginal sheet, even though the supporting surface of the platen isdiscontinuous.

According to the present invention there is provided a platen havinga-wall defining a reflective supporting surface for supporting a firstsheet of material in a predetermined relationship with a second materialto afford reproduction of graphic intelligence by producing an image ofthe first sheet on the second sheet by reflection of light directedtoward the supporting surface. The platen wall is formed with at leastone recess defining a discontinuity in the supporting surface whichrecess is defined by reflective wall means for reflecting incident lightthrough the recess in generally an even intensity across thediscontinuity. The wall means reflect incident light through thediscontinuity with generally the same intensity as light is reflected bythe supporting surface, thereby destroying the reflected image of therecessed area at the supporting surface.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will further bedescribed with reference to the accompanying drawings, wherein likenumbers refer to like parts in several views and wherein:

FIG. 1 is a schematic view of a portion of a copy machine incorporatinga support platen made in accordance with the present invention;

FIG. 2 is a perspective view of the platen according to the presentinvention that is incorporated in the machine of FIG.

FIG. 3 is an enlarged fragmentary sectional view taken approximatelyalong the lines 3-3 of FIG. 2; and

FIG. 4 is an enlarged fragmentary sectional view of an alternate methodof forming the area shown in FIG. 3.

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a portion of acopy machine for producing a copy of graphic intelligence on a first ororiginal sheet 10 which machine includes a platen 14 made according tothe present invention. The platen 14 provides a supporting surface 18for supporting the original sheet 10 for exposure to afford reproductionof graphic intelligence on the original sheet 10 by producing a latentimage in a second sheet or strip of translucent intermediate material 12from light directed toward the platen l4 and original sheet 10.

The original sheet 10 is fed from a delivery chute 15 by a suitable setof feed rollers 16 to the reflective supporting surface 18 of thecylindrical platen 14 so that the graphic intelligence on the originalsheet 10 is disposed opposite the supporting surface 18. The surface 18of the platen 14 is formed with means for interacting between the platenl4 and the original sheet 10, which may comprise a multiplicity oforifices 20 (illustrated in FIGS. 2 and 3) which communicate between anoriginal sheet 10 contacting the supporting surface 18 and a pressurebelow atmospheric pressure within the platen 14 produced by a pressureregulating means, thereby causing the sheet 10 to be pressed against thesurface 18 so that it will be moved by rotation of the platen 14.

The strip of photo-sensitive translucent intermediate material 12 isguided by a suitably positioned set of rollers 22 around a portion ofthe supporting surface 18 and may be moved in synchronism with theoriginal sheet 10 by drive means (not shown) past a light source 24within a reflector 25 which provides light directed toward thesupporting surface 18 and original sheet 10 for reflex exposure of theintermediate 12 from graphic intelligence on the original sheet 10. Theintermediate 12 is then led to a processing station on the machine (notshown) at which the intermediate is placed against the copy sheet andthe composite is heated; the residual light-sensitive reactant remainingat the imaged areas of the intermediate being transferred to andreactive with a coreactant in the copy sheet to produce a visiblereproduction of the original image on the copy sheet.

Through a suitable control system, the original sheet may be retained onthe supporting surface 18 and may be moved by continued rotation of theplaten 14 with the successive lengths of the intermediate material 12past the light source 24 for a predetermined number of times to producea desired number of copies, after which the pressure regulating meansprovides a higher than atmospheric pressure within the platen l4 andorifices 20 and in conjunction with a rotatable bar 27 (illustrated in aposition for removing a sheet from the supporting surface 18) directsthe original sheet 10 past a suitable set of guide rollers 26 to arecovery chute 28 on the machine.

FIG. 2 shows in greater detail the platen 14 which provides thereflective supporting surface 18 for supporting the original sheet 10between the surface 18 and the translucent intermediate 12. Thecylindrical platen 14 is comprised of a hollow cylindrical wall member29, circular end plates 30 and a hollow axle 32. The hollow axle 32 isconnected to the pressure regulating means which comprises a pump andvalve means, not shown, for establishing positive or negative airpressure within the platen 14, and in the orifices 20.

The supporting surface 18 of the cylindrical platen 14 includes means toprovide an essentially even reflection of light to all portions of theintermediate material 12 adjacent the supporting surface 18 despite thepresence of the orifices 20 thereon. This even reflectivity is importantto impart an even degree of reflex exposure to areas of the intermediate12 which are not separated from the supporting surface 18 by theoriginal sheet 10, so that if a copy sheet is larger than the originalsheet being copied, the image of the orifice 20 on the supportingsurface 18 will not be printed on portions of the copy sheet.

As illustrated in FIG. 3, a specially shaped recess 34 is formed in thewall member 29 about each orifice 20. Each recess 34 is formed bydeforming the wall member 29 to form a reflective converging wall meansor wall 36 which defines countersinking to provide a converging wallmeans or wall 42 disposed entirely at a predetermined angle (typically40) to a supporting surface. This method may be preferable where theplaten wall is too thick to be deformed.

The following is an example of physical parameters which have provedquite satisfactory in practicing the present invention: For an orifice20 to 44 which is 0.04 inches in diameter, a generally connical recessapproximately 0.06 inches deep and forming a circular discontinuity 0.20inches in diameter in the supporting surface is concentrically formedabout the orifice 20 or 44. The major portion of the reflective wall 36or 42 is disposed at an angle of 40 with the tangent to the supportingsurface. A recess 34 or 40 of these dimensions has been found toeffectively destroy the reflective image of the orifice 20 or 44 at thesupporting surface without causing a dimple in the original sheet and/orintermediate sheet positioned on the supporting surface due to apressure reduction of 12 inches of water below atmospheric pressurewithin the recess 34 or 40. The recess may be formed by countersinking(recess 40) or by deforming the platen wall (recess 34) by the use of apunch having a spherical tip with a radius of 0.06 inches which tipforms a corresponding radius at the base of the recess 34 and a slightradius at the juncture between the supporting surface and the majorportion of the reflective wall 36.

While the present invention is illustrated with respect to orificesformed in the surface of a platen, the invention may also be practicedto prevent prints on a copy sheet from recesses on a supporting surface18 required for the incorporation of other means interacting between theoriginal sheet 10 and the platen 14 such as switching or sensingdevices. Such devices may or may not contact the surface of theintermediate 12. If a portion of the device contacts the intennediate12, the conthe recess 34 about each orifice 20 with a major portion ofthe wall 36 disposed at a predetermined angle 38 (typically about with atangent at the supporting surface 18. The wall 36 reflects incidentlight through the discontinuity in the supporting surface 18 defined bythe recess 34 essentially in even distribution or even intensity acrossthe discontinuity. Thus, while some light directed toward the supportingsurface 18 will pass through each orifice 20, the light incident uponthe wall 36 is reflected in a pattern which will evenly expose thesection of intermediate material 12 positioned on the supporting surface18 adjacent the recess 34. The intensity of incident light reflected tothe intermediate 12 adjacent the recess 34 is generally the same as theintensity of light reflected from the balance of the supporting surface18, and is sufficiently close that a pattern will not be produced on thecopy sheet corresponding to the recessed areas 34 or the orifices 20.

Additionally, the wall means or wall 36 can be made more reflective thanthe supporting surface 18 so that it will reflect light to theintermediate 12 positioned above the recessed area 34 of essentially thesame intensity as the light reflected from the supporting surface 18.

A reflectivity for the supporting surface above 68 percent is generallycommercially acceptable for producing an even background on manypresently available copy papers.

The preferred reflectivity of the supporting surface is about 85 percentwhich corresponds to the reflectivity of the white bond paper typicallyused for an original sheet 10. This reflectivity' may be produced bycoating the supporting surface 18 and wall 36 with a white material suchas a suitable white paint.

If an electrically conductive supporting surface 18 is desired, thesurface of the platen may be formed of a properly reflective metal. Asan example, cadmium plated on the supporting surface 18 and walls 36 canproduce areflectivity of about 68 percent.

FIG. 4 illustrates an alternate method for forming a recessed area 40having a reflective wall 42 around an orifice 44 extending through aplaten wall. The wall 42 is formed as by tacting surface should have thesame reflectivity as the supporting surface 18. Also, the device must beshaped so as not to block incident light being reflected by thereflective wall means through areas of the discontinuity to anintermediate 12 positioned adjacent the recess and not contacted by thedevice. The angle of the wall and depth of the recessed area may requiresome adjustment for each such application. Additionally, the recess maybe in the form of a groove in the supporting surface rather than beinggenerally conical as illustrated.

Having thus described the present invention, what is claimed is:

What I claim is:

1. in a copy machine including a platen having a wall defining areflective supporting surface upon which a first sheet of material is tobe supported for exposure to afford the reproduction of graphicintelligence on said first sheet by producing a latent image on a secondsheet material from light directed toward the platen and first sheet,said wall being formed with a multiplicity of orifices in saidsupporting surface and communicating with means for regulating thepressure in said orifices, the improvement comprising:

said wall being formed with a plurality of recesses disposed about saidorifices, each said recess being defined by converging wall meansdefining a discontinuity in said supporting surface, said convergingwall means being reflective and being disposed for reflecting incidentlight through said discontinuity in even intensity across saiddiscontinuity, thereby destroying the reflected image of said orifice atsaid supporting surface.

2. The machine of claim 1 wherein each said converging wall meanscomprises a converging wall having a reflective surface surrounding saidorifice and disposed with respect to a tangent to said supportingsurface at generally a 40 angle.

3. The machine of claim 1 wherein said supporting surface and wall meanshave a reflectivity above 68 percent.

4. The machine of claim 2 wherein said supporting surface and saidreflective wall surface have a reflectivity essentially equivalent tothat of white bond paper.

5. The machine of claim 2 wherein said supporting surface and thesurface of said reflective wall comprise cadmium.

6. A platen having a wall defining a reflective supporting surface forsupporting a first sheet of material in a predetermined relationshipwith a second sheet material to afford reproduction of graphicintelligence by producing an image of said first sheet on said secondsheet material by reflection of light directed toward said supportingsurface, said platen being formed with at least one recess in said wall,said recess defining a discontinuity in said supporting surface andbeing defined by reflective wall means for reflecting incident lightthrough said discontinuity in generally an even intensity across saiddiscontinuity and with an intensity generally equal to light reflectedby said supporting surface, thereby destroying the reflected image ofsaid recess at said supporting surface.

7. A platen as described in claim 6 further comprising means located insaid recess for interacting between a said sheet on said supportingsurface and said platen.

8. A platen according to claim 7 wherein said means interacting betweena said sheet and said platen comprises an orifice formed in said platenwall and communicating between a said sheet on said supporting surfaceand a source of adjustable pressure.

9. The machine of claim 6 wherein each said converging wall meanscomprises a converging wall having a reflective surface surrounding saidorifice and disposed with respect to a tangent to said supportingsurface at generally a 40 angle.

10. The machine of claim 6 wherein said supporting surface and wallmeans have a reflectivity about 68 percent.

I STATES PATEfiT OiFICE A CER'II'FICATEv OF CORRECTION Patent No. 3, 77,6 Dated July 18, 1972 Inven tor(s)" Burt K. Sagawa' It is crtified thaterror appears in thehbove-idenfified patent and th at said LettersPatent are hereby corrected as shown below:

' Column 6, line 13, change "about" to above Signed and sealed this 2ndday of January 1973.

(SEAL) Attest:

EDWARD M-FLETCHER,JR. I ROBERT C SOTTSCHALK Attestingfifficef'Commisslonerof Paten ts- FORM PO-105O (10-69) USCOMM-DC 603764 69 *rus. sovzmmnrr nmmus orrlcc "I. o-us-an STATES PATEM OTTICE CERTIFICATE.OF CORRECTION Patent No. 3, 77, 6 Dated l 97 Inventofls) Burt K. SagawaIt is certified that error 'a ppears in the above-identified patent andthat said Letters Patent are hereby corrected as shown below: Column 6,line 13, Change about" to above Signed and sealed this Zndday of January1973.

(SEAL) "Attest:

EDWARD MtFLETCHER IR.

. ROBERT GOTTSCHALK Attesting .Officer Commissioner of Patents ORMPO-105O (10-69) USCOMM-DC 60376-i=69 h as sovimmim nmmcs OFFICE: nuo-us-aa4

1. In a copy machine including a platen having a wall defining areflective supporting surface upon which a first sheet of material is tobe supported for exposure to afford the reproduction of graphicintelligence on said first sheet by producing a latent image on a secondsheet material from light directed toward the platen and first sheet,said wall being formed with a multiplicity of orifices in saidsupporting surface and communicating with means for regulating thepressure in said orifices, the improvement comprising: said wall beingformed with a plurality of recesses disposed about said orifices, eachsaid recess being defined by converging wall means defining adiscontinuity in said supporting surface, said converging wall meansbeing reflective and being disposed for reflecting incident lightthrough said discontinuity in even intensity across said discontinuity,thereby destroying the reflected image of said orifice at saidsupporting surface.
 2. The machine of claim 1 wherein each saidconverging wall means comprises a converging wall having a reflectivesurface surrounding said orifice and disposed with respect to a tangentto said supporting surface at generally a 40* angle.
 3. The machine ofclaim 1 wherein said supporting surface and wall means have areflectivity above 68 percent.
 4. The machine of claim 2 wherein saidsupporting surface and said reflective wall surface have a reflectivityessentially equivalent to that of white bond paper.
 5. The machine ofclaim 2 wherein said supporting surface and the surface of saidreflective wall comprise cadmium.
 6. A platen having a wall defining areflective supporting surface for supporting a first sheet of materialin a predetermined relationship with a second sheet material to affordreproduction of graphic intelligence by producing an image of said firstsheet on said second sheet material by reflection of light directedtoward said supporting surface, said platen being formed with at leastone recess in said wall, said recess defining a discontinuity in saidsupporting surface and being defined by reflective wall means forreflecting incident light through said discontinuity in generally aneven intensity across said discontinuity and with an intensity generallyequal to light reflected by said supporting surface, thereby destroyingthe reflected image of said recess at said supporting surface.
 7. Aplaten as described in claim 6 further comprising means located in saidrecess for interacting between a said sheet on said supporting surfaceand said platen.
 8. A platen according to claim 7 wherein said meansinteracting between a said sheet and said platen comprises an orificeformed in said platen wall and communicating between a said sheet onsaid supporting surface and a source of adjustable pressure.
 9. Themachine of claim 6 wherein each said converging wall means comprises aconverging wall having a reflective surface surrounding said orifice anddisposed with respect to a tangent to said supporting surface atgenerally a 40* angle.
 10. The machine of claim 6 wherein saidsupporting surface and wall means have a reflectivity about 68 percent.